A physical model is proposed for the estimation of the screech amplitude in underexpanded supersonic jets. The model is based on the hypothesis that the interaction of a plane acoustic wave with stationary shock waves provides amplification of the transmitted acoustic wave upon traversing the shock. Powell's discrete source model for screech incorporating a stationary array of acoustic monopoles is extended to accommodate variable source strength. The proposed model reveals that the acoustic sources are of increasing strength with downstream distance. It is shown that the screech amplitude increases with the fully expanded jet Mach number. Comparisons of predicted screech amplitude with available test data show satisfactory agreement. The effect of variable source strength on the directivity of the fundamental (first harmonic, lowest frequency mode) and the second harmonic (overtone) is found to be unimportant with regard to the principal lobe (main or major lobe) of considerable relative strength, and is appreciable only in the secondary or minor lobes (of relatively weaker strength).


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    Title :

    Shock-refracted acoustic wave model for screech amplitude in supersonic jets


    Additional title:

    Akustisches Wellenmodell mit Brechung an Schockwellen zur Abschätzung der Geräuschamplitude in Überschall-Jets


    Contributors:
    Kandula, M. (author)

    Published in:

    AIAA Journal ; 46 , 3 ; 682-689


    Publication date :

    2008


    Size :

    8 Seiten, 10 Bilder, 48 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English